Laminated structure and adhesive therefor



Aug. 8, 1950 T P CAMP EI'AL LAMINATED STRUCTURE AND ADHESIVE THEREFORFiled July 24, 1943 Patented Aug. 8, 19

UNITED S Y Thomas 1'. Camp, Arlington Heights. and Chester N. Kolnlodin,Chicago, 111., assignors to United States Gypsum Company, Chicago, 11].,a -cor-- poration of Illinois Application July 24, 1943, Serial No.496,074

Claims.

This invention relates to a laminated structure. Though it isparticularly referred to the lamination of gypsum wallboard and likematerials, it can be readily adapted to other types wherever a waterresistant adhesive is particularly desirable.

It, therefore, is one of the many objects of this invention to provide alaminated structure comprising one or more plies of a gypsum wallboardand a water resistant adhesive in combination therewith, which iscapable of withstanding the deleterious effect of high humidity andrelatively high temperatures encountered in architectural structures.

A further object of this invention is to provide a water resistantadhesive and a method of making the same.

A still further object of this invention is to provide a laminatedstructure comprising wallboard adhesively secured to form a number ofplies, at a low cost and economy in manufacture.

These and other objects, expansions. adaptations, and variousmodifications will become apparent to those skilled in the art,particularly in view of the specifications underlying the principles ofthis invention as described. It, therefore,is obvious that suchextensions and various modifications are a part of the invention, andare intended to come within the spirit of the principles underlying thisinvention by the inventors.

Many laminated structures, which consist in the major part of acellulosic fiber, such as insulation board, pressed paper board, or thelike, as well as laminated structures comprising an exterior sheath ofcellulosic paper with a core of cementitious materials, like gypsum,cement, or the like, have a tendency when exposed to highly humidconditions and moisture to warp. It has been found, particularly inarchitectural structures located near bodies of water or highly humidland areas, that relatively large size sheets of laminated structures,such as described above, will frequently bow out to a considerableextent and sometimes fall 01! when used in ceiling and roofconstruction. It has been found that, for instance. gypsum wallboard inrelatively large size sheets, or lengths, will, under those conditions,sag- Thusit will not only destroy the beauty of the structure, but alsoimpair its usefulness.

After a considerable amount of study and experimentation, it was found,that this particular effect is caused by the use of unsuitable adhesive,or methods of attachment between the various plies used in building up alaminated wallboard 2 structure. Obviously, erection. methods can to alarge degree obliterate this condition, but such additionalprecautionary measures are expensive, and uneconomical in comparison tothe methods at erection used in connection with this inven- In marineconstruction the partitions between rooms consist of wallboard. Gypsumboard because of its fire resistant nature is frequently used. As anadditional fire measure. the gypsum wallboard is sometimes covered withmetal sheets. It has been found that under the high humidity conditionsencountered, the laminae frequently fall apart, buckle or otherwisebecome useless.

It has been found after very extensive experimentation and correlationof data that a good index to the suitability of various laminatedwallboard structures for use under the conditions specified above, canbe obtained by immersing the laminated structure in water maintained ata temperature of degrees Fahrenheit. It has been found that many of theselected adhesives which have been utilized for this purpose have brokendown within a very short time of several hours. Of course, there are anumber of resins, hardened glues containing an animal or a vegetableprotein set with various insolubilizers such as formaldehyde, or otherwell known materials, asphalts, etc., which will withstand the abovetest for a greater number of hours. But in each particular case, thereis some definite limitation which either prevents their use entirelywith the gypsum wallboard, insulation board, or like material. Gypsumwallboard. for instance, can be coated with a solution of athermo-setting resin, and then placed in a press. The necessary heat toset the thermo-setting resin must be applied from a practical point ofview by means of platens in contact with the surfaces of the gypsumboard. This means that the heat must travel through the core of thegypsum board, and finally emerge between the two gypsum boards or thejunction line containing the resin. Most thermo-setting resins requireconsiderable high heat, which decomposes the core of the gypsum board,and thereby destroys its strength and utility. Likewise, considerablepressure cannot be applied to insulation board, or gypsum wallboard. ormaterials of like nature, since it will compress them. and, in case ofgypsum board, crush the core and render the product useless for furtheruse. Cutback asphalt has also been tried, but under conditions of highhumidity and relatively high temperaturm encountered at the ceilings ofarchitectural structures, the asphalt has a tendency to flow, andthereby laminated structures either delaminate completely or sag. Forthe same rea-' gravated when metallic sheets are laminated to thewallboard, particularly gypsum board. The

metal sheets are impervious to moisture and ex-- cessive amounts ofmoisture that are used in certain types of adhesives cannot be absorbedby the wallboard surfaces. In addition these partitions when used inmarine construction are exposed to humid conditions. Because of thepreferential moisture absorption by the paper there is a marked tendencyin this type of construction to set up strains and stresses which startdelamination along all edges.

However, it has been found very unexpectedly that a mixture of asphaltemulsion and a particular type of unrefined, partially dextrinized,farinaceous paste in combination with the asphalt emulsion provides anadhesive which is not only entirely suitable for this type oflamination, but also withstands the most severe tests which a product ofthis type has encountered under actual construction conditions in thefield, as well as in the laboratory. The product of this invention, whenimmersed in water maintained at a temperature of 70 degrees Fahrenheit,is capable of maintaining its laminated structure until the ingredientsthemselves comprising the various plies fall apart.

It has been further found that when such failure occurs, as an example,in a laminated gypsum wallboard construction having cellulosic liners atthe interface of the lamination the lamination junction still retainsits life, and maintains its adhesive bond between the two adjacentcellulosic sheets or membranes although the wallboard core is destroyed;

This action is entirely unexpected, since emulsified asphalt alone, orthe partially dextrinized, farinaceous paste when used alone do not givecomparable results. Yetthe combination of these two materials when usedin the proportions specified hereinbelow have been able to withstandimmersions in water maintained at a temperature of 70 degrees for morethan twentyfour hours, and in many cases where the bond Formula 1 Percent Emulsified asphalt (clay type) 5 to 15 Partially dextrinized,farinaceous paste,

substantially as described below 5 to 15 Water to make up 100 Inpreparing this formulation, it is desirable to make a smooth paste byadding in increments 4 the partially dextrinized, farinaceous paste tothe water, and stirring it after each increment until the paste isuniformly smooth. This paste is then added to the asphalt emulsion, andthe two blended together with the gradual addition of a sufilcientamount of water to make up 100 per cent. Though this procedure can bevaried somewhat, it is desirable to follow it since a uniform mixture isobtained and can be readily spread upon the surface of the materials tobe laminated. It is desirable that the water used in the preparation ofthe adhesive should be relatively free of reagents which may have atendency to break the asphalt emulsion, or otherwise tfrail part adeleterious effect to this adhesive mix- The emulsified asphalt used inthe preparation 4 of this adhesive is of the clay type, and containsapproximately 45 to 50 per cent of asphalt. There are a number ofexcellent sources of this material on the market, and it has been foundthat the formulation sold under the mark N13HPC asphalt emulsion is butone of the many that can be used. The partially dextrinized, farinaceouspaste is a type of a corn flour paste, which is obtained by passing the"grits" from corn through a combination screw conveyor and a heaterwhich has a heating jacket to heat the grits" for a period of about onehour, with the steam in the jacket being maintained at a pressure of '60to 100 pounds per square inch. These heated grits are then put intoflake form by passing between a scraper knife, and a roll heated to 250degrees to 300 degrees Fahrenheit by the friction due to breaking up thegrits." The process of heating the corn grits causes a small portion ofthe same to be dextrinized. The resulting flakes are then ground up toform the paste, which is used in this invention in combination with theasphalt emulsion described herein above. For a more complete descriptionof the nature and analysis of the partially dextrinized, farinaceouspaste used herein, reference should be had to the Roos Patent No.2,044,401, issued June 16, 1936.

It has been found that a particularly useful formulation for use inlaminated gypsum wallboard structures comprises the following for--mula:

Formula 2 7 Per cent Emulsified asphalt (clay type) 5 Partiallydextrinized, farinaceous paste, substantially as described 10 Watermanufacture, though maintained to close thickness tolerances, variesimperceptibly in thickness throughout the area of the board. Obviouslyunder such conditions, the height of the ridge of the adhesive that isapplied to the surface must be sufficient to contact the abuttingsurface. Therefore, the minimum height that an adhesive can be appliedis controlled to a marked degree by the imperceptible variation in thethickness of the gypsum wallboard. Under the above com ditions andslight variations in the thicknesses of gypsum wallboard, it isnaturally desirable that the adhesive be applied in the form of ridges,rather than be applied by means of conventional coater rolls or knives.

The drawing forming a part of this application for Letters Patent,illustrates the preferred type of glue application. For purposes ofillustration only and not as a limitation of the principles underlyingthis invention, a single lamination is shown illustrating the ridgemethod of application of the adhesive composition of this invention incombination with gypsum wallboard. II and I! represent one or morelayers of gypsum wallboard or other materials to be laminated. 18represents the composition of this invention applied as ridges acrossthe face of the sheet II. It is obvious that it can be applied on thecontacting face of the sheet l3 or on any other sheets used in making upthe combination. Likewise it is self-evident that equivalent means ofapplying the composition may be used. For instance dabs or spots of theadhesive composition may be placed about the surface of either one orboth of the combination of the partially dextrinized,

farinaceous paste, substantially as described herelnabove, and anemulsified asphalt of the clay type. A number of different theories havebeen postulated, but it is not the intention of the inventors to bebound thereby, since obviously various expansions, modifications,adaptations, as well as variations of the principles underlying thisinvention, as defined in the hereto appended claims and substantiallydescribed hereinabove,

, can be used.

We claim:

1. A laminated structure comprising a plurality of gypsum boards, eachof the said gypsum boards composed of a gypsum core and cellulosic papersurfacings thereon and an adhesive between said boards, the saidadhesive comprising an emulsifled asphalt and a partially dextrinizedfarinaceous paste consisting wholly of heat treated corn ts.

2. In the laminated structure of claim 1, wherein the said emulsifiedasphalt is an emulsified asphalt of the clay type.

3. In the laminated structure of claim 1, wherein the said adhesivecomprises the following ingredients substantially in the ranges shownbelow:

' Per cent Emulsifled asphalt 5 to 15 Partially dextrinized, farinaceouspaste derived wholly from heat treated corn grits 5 to 15 Water to make100 4. An adhesive whose products of interaction are capable ofwithstanding immersion without dissolution for at least 24 hours inwater main- };gined at a temperature of degrees F. compris- Per centEmulsified asphalt 5 to 15 Partially dextrinized farinaceous pastederived wholly from heat treated corn grits 5 to 15 Water to make 5. Inthe adhesive of claim 4, wherein the said emulsified asphalt is anemulsified asphalt of the clay type.

- THOMAS P. CAMP.

CHESTER N. KOLMODIN.

REFERENCES CITED The following references are oi record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,329,232 Erler Jan. 27, 19201,353,510 Baumgartel Sept. 21, 1920 1,474,657 Walper Nov. 20, 19231,507,332 Buttress et a] Sept. 2, 1924 1,568,314 Buttress et a1. Jan. 5,1926 1,664,601 Ellis Apr. 3, 1928 1,793,810 Levin Feb. 24, 19311,870,439 Birdsey Aug. 9, 1932 1,914,345 Roos June 13, 1933 2,014,406Weed Sept. 17, 1935 2,017,022 Roos Oct. 8, 1935 2,035,122 Fulton Mar.24, 1936 2,044,401 Roos June 16, 1936 2,051,025 Bauer Aug. 18, 19362,282,177 Dike et al May 5, 1942 2,366,943 Treadway Jan. 9, 1945

1. A LAMINATED STRUCTURE COMPRISING A PLURALITY OF GYPSUM BOARDS, EACH OF THE SAID GYPSUM BOARDS COMPOSED OF AGYPSUM CORE AND CELLULOSIC PAPER SURFACINGS THEREON AND AN ADHESIVE BETWEEN SAID BOARDS, THE SLAID ADHESIVE COMPRISING AN EMULSIFIED ASPHALT AND A PARTIALLY DEXTRINIZED FARINACESOUS PASTE CONSISTING WHOLLY OF HEAT TREATED CORN GRITS. 